1. Field of the Invention
The present invention relates to a multi-pole circuit breaker, and more particularly, to a multi-pole circuit breaker, which can ensure the equilibrium of contact forces between contactors in a single pole breaking unit relatively far from a switching mechanism and the reliability of a switching operation between the contactors.
2. Description of the Conventional Art
In general, a circuit breaker is an electrical device that protects a load and a line by manually or automatically breaking the line in the event of an abnormal condition such as an overload and short-circuiting of the line.
FIG. 1 is a perspective view illustrating a conventional multi-pole circuit breaker. FIG. 2 is an exploded perspective view illustrating a conventional multi-pole circuit breaker. FIG. 3 is a side view illustrating a conventional multi-pole circuit breaker. FIG. 4 is a perspective view showing the deformation of a driving shaft in a conventional multi-pole circuit breaker.
As illustrated in FIGS, 1 to 4, the conventional multi-pole circuit breaker 1 includes four single pole breaking units 10a, 10b, 10c, and 10d, that is, a single pole breaking unit 10a of R phase, a single pole breaking unit 10b of S phase, a single pole breaking unit 10c of T phase, and a single pole breaking unit 10d of N phase.
Each of the single pole breaking units includes a case 20 having a space, a plurality of contactors 40 including fixed contactors 41 installed in the case 20 with a predetermined distance and a movable contactor 42 rotatably disposed between the fixed contactors 41 by shafts 53, a trip mechanism (not shown) for tripping the circuit breaker by detecting a large current flowing through the circuit, a switching mechanism 50 automatically operated by the trip mechanism or manually operated by operating a handle 51, for separating the movable contactor 42 from the fixed contactors 41 thereby cutting off a circuit, and an arc extinguishing mechanism 60 for extinguishing arc gas of a high temperature and a high pressure generated between movable contactor 42 and the fixed contacts 41 at the time of switching a circuit.
The switching mechanism 50 includes a handle 51, an upper link (not shown) coupled to the trip mechanism, a lower link (not shown) coupled in conjunction with the lower part of the upper link, and driving shafts 52 for commonly connecting the lower link and the shaft 53 of each single pole breaking unit so that the shaft 53 of each single pole breaking unit can rotate in conjunction with the lower link.
In the thus-constructed conventional multi-pole circuit breaker, when a normal current flows on a circuit, the movable contactor 42 is in contact with fixed contactors 41 thereby to maintain a closed circuit state.
On the other hand, when a large current flows on the circuit abnormally while a circuit is in an ON state, the circuit breaker is tripped, At this time, the upper link and the lower link are rotated. As the lower link is rotated, the shaft 53 coupled thereto through the driving shaft 52 rotates in a clockwise direction. At this time, the movable contactor 42 is separated from the fixed contactors 41 to thereby maintain an opened circuit state.
However, in the conventional multi-pole circuit breaker, the switching mechanism 50 is not installed at the middle of the circuit breaker but installed biased to one side, that is to say, at the single pole breaking unit 10b of S phase corresponding to the second right one, as illustrated in FIGS. 1 and 2, of the four single pole breaking units 10a, 10b, 10c, and 10d to thereby make unbalanced the force applied to each of the single pole breaking units 10a, 10b, 10c, and 10d by the switching mechanism 50.
Subsequently, there occurs a problem that, as shown in FIG. 4, end portions of the driving shafts 52 are deformed as they are bent in a clockwise direction. Hence, the shaft installed at the single pole breaking unit 10d of N phase has a smaller amount of rotation as compared to the shafts installed at the other single pole breaking units 10a, 10b, and 10c, and as a result, the contact and separation performance between the fixed contactors 41 and the movable contactor 42 and the reliability of the product are deteriorated.